Effects of Synoptic Surveillance on model forecasts for
17 November 1999 1200 UTC
LENNY.


QuickTime movie of DLM wind model forecasts
QuickTime movie of DLM wind data increments


TRACK AND INTENSITY PERFORMANCE

TRACK (km)
MODEL12 h24 h36 h48 h60 h72 h84 h96 h108 h120 h
AVNN246.273.306.368.475.632.824.852.865.983.
AVAL120.193.255.300.399.574.826.901.875.885.
%IMP51%29%17%18%16%9%0%-6%-1%10%
GFNO77.62.201.391.622.884.1203.1415.1630.2038.
GFAL54.67.172.403.644.914.1258.1455.1717.2030.
%IMP30%-8%14%-3%-4%-3%-5%-3%-5%0%
INTENSITY (kt)
MODEL12 h24 h36 h48 h60 h72 h84 h96 h108 h120 h
AVNN-96.-83.-50.-35.-20.-11.-6.7.20.17.
AVAL-96.-81.-49.-35.-23.-15.5.10.16.16.
%IMP0%2%2%0%-15%-36%17%-43%20%6%
GFNO-25.-17.10.23.41.38.49.57.62.63.
GFAL-20.-10.12.27.41.35.53.55.60.59.
%IMP20%41%-20%-17%0%8%-8%4%3%6%
SHNO-12.-7.19.21.27.11.14.18.17.14.
SHAL-13.-8.19.20.26.10.12.15.14.11.
%IMP-8%-14%0%5%4%9%14%17%18%21%
DSNO-12.-7.19.21.27.11.14.18.17.14.
DSAL-13.-8.19.20.26.10.12.15.14.11.
%IMP-8%-14%0%5%4%9%14%17%18%21%

Landfall forecasts

17/1800 UTC 17.4N 64.8W St. Croix, USVI 6 h into the forecast
MODELLATLONTIMEERRORLOCATION
AVNN17.9565.9935.5140.0 Hacienda San Isidro, PR
AVAL17.5165.3722.561.6 Near Frederiksted, St. Croix, USVI
%IMP44%56%
GFNO17.6464.3619.053.7 Christiansted, St. Croix, USVI
GFAL17.7064.3619.057.3 Christiansted, St. Croix, USVI
%IMP0%-7%
18/1800 UTC 18.0N 63.3W St. Martin 30 h into the forecast
MODELLATLONTIMEERRORLOCATION
AVNN17.9565.9935.5284.3 Hacienda San Isidro, PR
AVAL18.0865.4731.5229.4 Esperanza, Vieques, PR
%IMP73%19%
GFNO18.6063.9227.093.4 Near Anegada, British Virgin Islands
GFAL18.5864.0128.598.8 Near Anegada, British Virgin Islands
%IMP50%-6%
19/0000 UTC 18.1N 63.1W Anguilla 36 h into the forecast
MODELLATLONTIMEERRORLOCATION
AVNN17.9565.9935.5305.8 Hacienda San Isidro, PR
AVAL18.4065.5036.0255.4 Soroco, PR
%IMP100%16%
GFNO18.6063.9227.0102.8 Near Anegada, British Virgin Islands
GFAL18.5864.0128.5109.8 Near Anegada, British Virgin Islands
%IMP17%-7%
19/0600 UTC 18.0N 62.9W St. Barthelemy 42 h into the forecast
MODELLATLONTIMEERRORLOCATION
AVNN17.9565.9935.5326.6 Hacienda San Isidro, PR
AVAL18.4065.5036.0278.0 Soroco, PR
%IMP8%15%
GFNO18.6063.9227.0126.6 Near Anegada, British Virgin Islands
GFAL18.5864.0128.5133.7 Near Anegada, British Virgin Islands
%IMP10%-6%
20/0000 UTC 17.3N 61.8W Antigua 60 h into the forecast
MODELLATLONTIMEERRORLOCATION
AVNN17.9565.9935.5449.6 Hacienda Sann Isidro, PR
AVAL18.4065.5036.0409.9 Soroco, PR
%IMP2%9%
GFNO18.6063.9227.0266.6 Near Anegada, British Virgin Islands
GFAL18.5864.0128.5273.5 Near Anegada, British Virgin Islands
%IMP5%-3%

Figure 1. NCEP 850 - 200 hPa mean wind analysis for 17 November 1999 1200 UTC (Hurricane Lenny).

Figure 2. Track forecasts for the no dropwindsonde (NO or NN) and the all dropwindsonde (AL) runs for the AVN and GFDL models initialized on 17 November 1999 1200 UTC. The best track is shown in black.

Figure 3. Initial condition differences in the 850 - 200 hPa mean wind between the no and all dropwindsonde cases for 17 November 1999 1200 UTC.

Figure 4. 12-h forecast differences in the 850 - 200 hPa mean wind between the no and all dropwindsonde cases for 17 November 1999 1200 UTC.